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Photonics Technology Letters, IEEE

Issue 9 • Date May1, 2008

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Displaying Results 1 - 25 of 38
  • [Front cover]

    Publication Year: 2008 , Page(s): C1
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    Freely Available from IEEE
  • IEEE Photonics Technology Letters publication information

    Publication Year: 2008 , Page(s): C2
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  • Table of contents

    Publication Year: 2008 , Page(s): 665 - 666
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  • Noise Correlation, Regenerative Amplification, and the Linewidth Enhancement Factor of a Vertical-Cavity Surface-Emitting Laser

    Publication Year: 2008 , Page(s): 667 - 669
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB) |  | HTML iconHTML  

    This letter reports on amplitude and frequency noise correlation measurements as well as on optical injection experiments related to the linewidth enhancement factor a of a vertical- cavity surface-emitting laser (VCSEL). It is shown that the correlation in VCSELs is not dominated by alpha; consequently, such experiments yield very little information on its value. Measuring the regenerative amplification of a weak injected optical probe turned out to be a robust approach that can not only give accurately the relaxation oscillation frequency and the damping rate but a good estimate of alpha as well. Finally, these experiments are combined with previously published data to increase the number of techniques applied to the measurement of alpha of a single semiconductor laser up to 11. View full abstract»

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  • Spectrally Efficient Compatible Single-Sideband Modulation for OFDM Transmission With Direct Detection

    Publication Year: 2008 , Page(s): 670 - 672
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (371 KB) |  | HTML iconHTML  

    A combination of orthogonal frequency-division multiplexing (OFDM) and compatible single-sideband modulation (CompSSB) using a standard direct-detection scheme is suggested to overcome chromatic dispersion without explicit compensation. Since the proposed type of SSB modulation does not require a spectral gap between optical carrier and subcarriers, it is highly spectrally efficient and the complexity in the analogue part is reduced compared to known direct-detection schemes for OFDM. View full abstract»

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  • Opening of Hybrid Bandgaps in Two-Dimensional Photonic Crystals of Pb(Mg _{1/3} Nb _{1/3} )O _{3} –PbTiO _{3} Having Very Low Refractive Index Contrast

    Publication Year: 2008 , Page(s): 673 - 675
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (485 KB) |  | HTML iconHTML  

    The effect of anisotropy on two-dimensional photonic crystals of hexagonally arranged Pb(Mg1/3Nb1/3)O3-PbTiO3 (PMNT) rods in air background was analyzed using a finite-difference time-domain method. The refractive index contrast between PMNT (n = 2.47) and air is low compared to conventional semiconductor-air photonic crystals. Yet, hybrid (polarization-independent) photonic bandgaps were achieved for anisotropic PMNT rods by adjusting the structural parameters and the anisotropy. The maximum bandwidth found was 20 nm. It was possible to engineer the center wavelength of this bandgap to 980, 1300, and 1550 nm, for potential applications as switches, electrooptic filters, and modulators in this region. View full abstract»

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  • Proposal for Compact Optical Filters Using Large Index Step Binary Supergratings

    Publication Year: 2008 , Page(s): 676 - 678
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (321 KB) |  | HTML iconHTML  

    Compact optical filters are proposed using an aperiodic grating of fixed element size [i.e., a binary supergrating (BSG)] with a large refractive index step. These filters allow for almost arbitrary wavelength filtering, yet they are more compact than previous demonstrations of BSG. The filters are designed using a combination of Boolean particle swarm optimization (B-PSO) and a one-dimensional transfer matrix method. To demonstrate the compact device size, several 50-mum-long single-wavelength transmission filters are demonstrated theoretically, each having a different wavelength while using the same structural parameters. A multiwavelength filter is also proposed in an 80-mum-long structure to show the versatility of the large refractive index step BSG. A genetic algorithm is substituted for the B-PSO; however, B-PSO shows better performance here. This work may be applied to produce compact optical filters for intrachip optical networks and compact tunable lasers, while using existing single-step photolithography processes. View full abstract»

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  • Reliable Wavelength-Division-Multiplexed Passive Optical Network Using Novel Protection Scheme

    Publication Year: 2008 , Page(s): 679 - 681
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB) |  | HTML iconHTML  

    A novel, reliable wavelength-division-multiplexed passive optical network (WDM-PON) with self-protection capability is proposed. By utilizing the routing characteristics of N x N arrayed waveguide grating, the proposed architecture can provide automatic protection against any fiber cut between central office and optical network unit (ONU). Compared with the conventional schemes, this scheme adopts colorless ONUs, thus leading to a decrease in the costs of operation, administration, and maintenance, as well as the production cost. Without the performance degradation, the proposed WDM-PON scheme can offer a reliable network service. In the experiment, the protection performance was demonstrated in the carrier-distributed 1.25-Gb/s WDM transmission over 20-km single-mode fiber. View full abstract»

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  • Gamma-Ray Irradiation-Enhanced Wet-Etching of Proton-Exchanged Lithium Niobate

    Publication Year: 2008 , Page(s): 682 - 684
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (275 KB) |  | HTML iconHTML  

    Gamma-ray irradiation-enhanced wet-etching of proton-exchanged Z-cut Y-propagating LiNbO3 is presented. The etched ridge height of a sample with gamma-ray irradiation of intensity 650 krad/h on a LiNbO3 substrate for 30 min is three times larger than that without. Moreover, experimental results show the propagation loss values of Ti-indiffused LiNbO3 waveguides fabricated on the irradiated ridge structures are only slightly larger than those on the nonirradiated ones. View full abstract»

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  • All-Optical Subcarrier Demodulation in Up-Link of WDM mm-Wave Radio-Over-Fiber System

    Publication Year: 2008 , Page(s): 685 - 687
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (371 KB) |  | HTML iconHTML  

    We have proposed and experimentally demonstrated a scheme of all-optical broadband subcarrier demodulation in the up-link of wavelength-division-multiplexing (WDM) millimeter-wave radio-over-fiber systems. In this scheme, the subcarriers of all the WDM channels can be demodulated by only one optical demodulation module, hence its cost can be reduced remarkably. Because of its all-optical implementation, it can offer more bandwidth. The radio-frequency power degradation introduced by the channel dispersion is also avoided in this scheme even when the conventional simple double-sideband modulation method is employed in the base stations. View full abstract»

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  • A Proposal of Temperature Sensing Using a Thin-Film Bandpass Filter and Dual-Wavelength Push–Pull Reflectometry

    Publication Year: 2008 , Page(s): 688 - 690
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (171 KB) |  | HTML iconHTML  

    A new temperature sensing system, which utilizes a thin-film bandpass filter deposited on an optical fiber end face and dual-wavelength push-pull reflectometry, is proposed. The system has the following advantages over the fiber Bragg grating sensor: it can observe the temperature in a localized small area and it gets rid of microcrack growth caused by stripping of cover coating from a fiber. The feasibility of the system has been verified by simulation. View full abstract»

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  • Polarization-Independent Optical Demultiplexing Using XPM-Induced Wavelength Shifting in Highly Nonlinear Fiber

    Publication Year: 2008 , Page(s): 691 - 693
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (382 KB) |  | HTML iconHTML  

    Polarization-independent all-optical demultiplexing of 160-Gb/s optical time-division-multiplexed data based on cross-phase-modulation-induced wavelength shifting in highly nonlinear fiber (HNLF) has been experimentally demonstrated with a maximum power penalty of 0.8 dB due to signal polarization variations. The method uses a simple and easy-to-implement single-path polarization-diversity scheme by placing a short piece of polarization-maintaining fiber before the HNLF. View full abstract»

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  • A Programmable 8-bit Optical Correlator Filter for Optical Bit Pattern Recognition

    Publication Year: 2008 , Page(s): 694 - 696
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (314 KB) |  | HTML iconHTML  

    We demonstrate a compact reconfigurable 8-bit optical matching filter fabricated using 4% delta high-index-contrast silica-on-silicon waveguides. This planar lightwave circuit is based on an eighth-order tap-and-delay finite impulse response architecture. Multimode interference-based splitters/combiners along with variable optical attenuators and phase shifters allow us to tune and dynamically reconfigure all the taps and delays (filter coefficients) in the filter using a simple automated algorithm. The filter is designed to recognize 8-bit patterns in 40-Gb/s data streams and we demonstrate its working principle by successfully correlating 8-bit binary phase-shift-keyed patterns. View full abstract»

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  • Broadband Polarizers Using Dual-Layer Metallic Nanowire Grids

    Publication Year: 2008 , Page(s): 697 - 699
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (403 KB) |  | HTML iconHTML  

    Broadband polarizers functioning in an extremely wide wavelength range from 0.3 to 5 mum were developed based on structural design and numerical simulation. By properly selecting the dual-layer nanowire grids including metal materials, grid periods, grid thicknesses, and substrate materials, broadband polarizers could be developed to realize high optical performance. We proposed a broadband polarizer using aluminum nanowire grids on a magnesium fluoride substrate with 80-nm square grids. The proposed polarizer can reach an extinction ratio from 47 to 70 dB and a transmission efficiency from 38% to 94% in the wide wavelength range. View full abstract»

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  • Link Reliability Improvement for Optical Wireless Communication Systems With Temporal-Domain Diversity Reception

    Publication Year: 2008 , Page(s): 700 - 702
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB) |  | HTML iconHTML  

    We experimentally demonstrate a simple temporal- domain diversity reception (TD-DR) scheme to enhance the reliability of optical wireless transmission links corrupted by atmospheric turbulence (AT) effects. Both nonreturn-to-zero and Manchester encoded on-off-keying modulation schemes are studied in laboratory environments at a 1.25-Gb/s data rate. AT effects are emulated as a slowly varying log-normal intensity variation for the received signal. System bit-error ratio is tracked for the performance evaluation, and results show that the outage probability due to the AT-induced intensity fluctuation for a 1.25-Gb/s link using Manchester coding is reduced from 3.2%plusmn0.1% to <0.1%, when the TD-DR is employed. View full abstract»

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  • Current Spreading and Blocking Designs for Improving Light Output Power from the Vertical-Structured GaN-Based Light-Emitting Diodes

    Publication Year: 2008 , Page(s): 703 - 705
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (227 KB) |  | HTML iconHTML  

    In this work, use of localized Ti deposition associated with a transparent indium-zinc-oxide (IZO) layer is proposed to serve as Schottky current blocking and current spreading layer, respectively. In addition, an inductively coupled plasma (ICP) mesa etching on the surface layer (n-GaN) of regular vertical-conducting metal-substrate GaN-based light-emitting diodes (VM-LEDs) is also proposed to further enhance current spreading of the device. Through a two-dimensional device simulator, the calculated results indicate that significant avoidance of the current-crowding effect under cathode contact pad could be obtained once the n-GaN layer etching depth and width, IZO thickness, and Schottky current blocking width have been optimized. In experiments, 1000 m 1000 m GaN-based blue LEDs with an ICP mesa etching of 250 m in width and 2 m in depth on the surface n-GaN layer, 200 m in Schottky current blocking width, and a 300-nm-thick IZO layer have the been successfully fabricated. As compared to the regular VM-LEDs without the use of the present technology, typical improvement in light emission uniformity and light output power by about 6% and 38% at an injection current of 350 mA have been obtained. View full abstract»

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  • Precompensation for Narrow Optical Filtering of 10-Gb/s Intensity Modulated Signals

    Publication Year: 2008 , Page(s): 706 - 708
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (709 KB) |  | HTML iconHTML  

    Signals in spectrally efficient optical networks can be distorted by the narrowing of the overall bandwidth that occurs when optical add-drop multiplexers are concatenated. In this letter, it is demonstrated that the performance implications of this bandwidth narrowing can be mitigated by precompensation using arbitrary optical waveform generation. The synthesis of the required voltage waveforms for a dual-drive Mach-Zehnder modulator reduces the penalty in receiver sensitivity due to narrow optical filtering from 6.5 to 1.9 dB. Simultaneous precompensation for fiber dispersion is also demonstrated. View full abstract»

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  • Large-Format Voltage-Tunable Dual-Color Midwavelength Infrared Quantum-Well Infrared Photodetector Focal Plane Array

    Publication Year: 2008 , Page(s): 709 - 711
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB) |  | HTML iconHTML  

    We report a large-format (640 times 512) voltage-tunable quantum-well infrared photodetector (QWIP) focal plane array (FPA) for dual-color imaging in the midwavelength infrared (3-5 mum) band. Voltage-tunable spectral response has been achieved through series connection of two eight-well stacks of AlGaAs-InGaAs epilayers grown by molecular beam epitaxy on GaAs substrate. The peak responsivity wavelength of the detectors is shifted from 4.1 mum (color 1) to 4.7 mum (color 2) as the bias is increased within the limit applicable by commercial read-out integrated circuits. The operability of the FPA is ~99.5% with noise equivalent temperature differences of ~60 and 30 mK (f/1.5) in color modes 1 and 2, respectively. To our knowledge, this is the first large-format voltage-tunable dual-color QWIP FPA reported for midwavelength thermal imaging. View full abstract»

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  • One-to-Many and Many-to-One Optical Chaos Communications Using Semiconductor Lasers

    Publication Year: 2008 , Page(s): 712 - 714
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (197 KB) |  | HTML iconHTML  

    A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications. View full abstract»

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  • Communication Limits Due to Photon Detector Jitter

    Publication Year: 2008 , Page(s): 715 - 717
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (391 KB) |  | HTML iconHTML  

    Detector jitter, the random delay from the time a photon is incident on a single-photon-counting detector (SPD) to the time an electrical pulse is produced in response to that photon, is characterized for a number of SPDs. The jitter is modeled as a weighted sum of Gaussians. The performance in detector jitter is measured by determining the capacity of a communications channel utilizing a given detector. It is observed that the loss, measured as the ratio of the signal power required to achieve a specified capacity in the presence of jitter to that in the absence of jitter, goes as the square of the normalized jitter standard deviation (the standard deviation of the jitter in slotwidths). The loss is small when the normalized jitter is less than one, and becomes significant beyond that point. This loss must be taken into account when evaluating detectors for very high throughput channels. View full abstract»

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  • A Proposal for Enhanced Parametric Amplification in Periodic Superstructure Fiber

    Publication Year: 2008 , Page(s): 718 - 720
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (173 KB) |  | HTML iconHTML  

    We designed a multidefect nonlinear superstructure fiber (SF) to serve as the gain medium of optical parametric amplification. In both theoretical derivation and simulation results, the signal amplification proved to achieve enhancement at certain frequencies where the local field intensities were increased or the slow group velocities of the modes were greatly slowed down on the band edges to offset the negative effect raised by large wave vector mismatching. View full abstract»

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  • Proposal to Achieve 1 Tb/s per Wavelength Transmission Using Three-Dimensional LDPC-Coded Modulation

    Publication Year: 2008 , Page(s): 721 - 723
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (378 KB) |  | HTML iconHTML  

    We propose a three-dimensional (3-D) low-density parity check (LDPC)-coded modulation scheme that enables optical transmission beyond 320 Gb/s in aggregate rate using currently available commercial components operating at 40 giga-symbols/s. The proposed scheme introduces significant performance improvement of up to 4.1 dB at a bit-error ratio of 10-9 over the corresponding two-dimensional scheme. In addition, by using LDPC-coded 1024-3D-constellation it is possible, at least in theory, to achieve beyond a total of 1-Tb/s transmission using transmission equipment operating at 100 giga-symbols/s, once it reaches the maturity of 40-Gb/s systems. View full abstract»

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  • Electrooptical Modulator at Telecommunication Wavelengths Based on GaN–AlN Coupled Quantum Wells

    Publication Year: 2008 , Page(s): 724 - 726
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    We report on the demonstration of an intersubband (ISB) coupled quantum-well modulator operating at room temperature and telecommunication wavelength using a GaN-AIN quantum-well structure. The optical modulation is shown to result from electron tunneling between the wells. Stark shifting of the ISB absorption is observed. The maximum modulation depth is 0.79% at lambda= 2.3 mum and 0.18% at lambda= 1.37 mum for a mesa device with only 151-nm interaction length. We show that by reducing the mesa size down to 15 times 15 mum2, optical modulation bandwidth as large as 3 GHz can be obtained. View full abstract»

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  • High-Power Continuous-Wave Single-Longitudinal-Mode Operation of an Optically Pumped DFB Laser at \lambda \sim 3.64~ \mu m

    Publication Year: 2008 , Page(s): 727 - 729
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    High-power continuous-wave (CW) single-longitudinal-mode emission at 3.64 mum is obtained from an optically pumped distributed-feedback (DFB) laser. The Bragg stopband and two degenerate DFB modes are observed at certain pump powers. The laser incorporates 14 InAs-InGaSb-InAs type-II quantum wells imbedded in an InGaAsSb waveguide. The index-coupled 1-D grating is fabricated in the top clad using interference lithography and plasma etching. A 110-mum-wide stripe from a 1.9-mum CW laser provides both optical pumping and gain guiding. Record high output power of more than 560 mW per side is obtained at 80 K. The wavelength is tunable over a 6.8-nm range by varying the pump power from 1 to 8.1 W. View full abstract»

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  • Novel Grating Design for Out-of-Plane Coupling With Nonuniform Duty Cycle

    Publication Year: 2008 , Page(s): 730 - 732
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    We propose a waveguide grating coupler with nonuniform duty cycle for the out-of-plane coupling of light from a planar waveguide to an optical fiber, and evaluate the optical performances based on Bloch-wave analysis. The mode profile and focusing performance of the diffracted output beam are investigated in terms of the duty cycle to improve optical coupling efficiency. View full abstract»

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Aims & Scope

This letters journal addresses all aspects of the IEEE Photonics Society Constitutional Field of Interest with emphasis on photonic/lightwave components and applications, laser physics and systems and laser/electro-optics technology.

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Meet Our Editors

Editor-in-Chief
Dr. Seb J. Savory
University College London